Heretofore, compounding polyacetal resin with a sufficient amount of electrically conductive carbon black has been practiced as a method for imparting electrical conductivity to the resin. Examples of electrically conductive polyacetal resin compositions are disclosed in U.S. Pat. Nos. 4,391,741 and 4,555,357. A useful and commercially available electrically conductive carbon black which has been used to form electrically conductive polyacetal resin has been KETJENBLACK EC (a product of Akzo Chemie). A typical conductive polyacetal formulation contains an oxymethylene copolymer having a melt index of 27.0 g/10 min. and 6 wt. % of the KETJENBLACK EC electrically conductive carbon black. While such formulation provides excellent conductivity, the addition of the carbon black significantly reduces the toughness and flexibility of the final molded product. In many applications where higher flexibility is required such as for snap fitting the molded polyacetal resin parts, breakage occurs because of poor elongation and low practical impact strength. Moreover, the need to use a 6 wt. % level of the electrically conductive carbon black to provide sufficient electrical conductivity to the polyacetal resin increases the melt viscosity of the polyacetal resin, degrading melt flow and thus, making it more difficult to form components from the resin by injection molding techniques.
One known method to improve the impact strength of polyacetal resins is by the incorporation of polyurethanes thereto. For example, commonly assigned U.S. Pat. No. 4,665,126 and European Patent Application No. 167,369, published Jan. 8, 1986 disclose oxymethylene polymer molding compositions having enhanced impact resistance by the incorporation of elastomeric polyurethanes. The patents are not directed to electrically conductive polyacetal resin compositions and, thus, do not address what effect the addition of polyurethane may have on electrical conductivity.